Stitch-forming mechanism for sewing machines



S. ZONIS July 29, 1941.

STITCH-FORMING MECHANISM FOR SEWING MACHINES Filed April 9; 1940 2 Shee'ts-Sheet 1 S. ZONIS July 29; 1941.

STITCH-FORMING MECHANISM FOR SEWING MACHINES Filed April 9, 1940 2 Sheets-Sheet 2 gwvegoz/ jdnis W wweom %"77 9% Patented July 29, 1941 STITCH-FORMING mo MECHANISM FOR SEW- MACHINES Sydney Zonis, Stratford, Conm, assignor to The Singer Manufacturing Company, Elizabeth, N. J a corporation of New Jersey Application April 9, 1940, Serial No. 328,610

4 Claims. (Cl. l12-184) This invention relates to stitch-forming mech- I anisms of lock-stitch sewing machines and has for its primary object to provide improved means for casting needle-thread loops about a looplocking or bobbin-thread.

More specifically. the invention aims to improve the quality of the stitches formed by a lockstitch sewing machine, and particularly in machines adapted for sewing leather" and similar materials, by creating conditions favorable to proper setting of stitches and minimizing the formation of loose loops of thread and abnormal knots at the under side of the work.

The invention consists in the loop-taker mechanism and the thread-carrier oscillating means employed in combination therewith as hereinafter described in connection with the accompaying drawings which illustrate a preferred embodiment of the invention and in which:

Fig. 1 is a front side elevation, partly in vertical section, of a sewing machine containing the present improvement. Fig. 2 is a front end elevation, partly in vertical section, showing the work-supporting post of the sewing machine and including the lower portions of the needleand 'presser-bars, the front end cover-plate of the post being removed. Fig. 3 represents a perspec tive view of the thread-case and of the threadcase oscillating mechanism associated therewith, detached from the machine. Fig. 4 represents a perspective view of the throat-plate of the machine. Figs. 5, 6 and 7 are enlarged top-plan views of the loop-taker and of the free end portion of an arm of the thread-case oscillating lever in successively different positions of said arm during a stitch-forming cycle. Figs. 8, 9 and 10 represent enlarged views of the throat-plate needle-aperture (in dot-dash lines) and of the threads in said aperture (in cross-section) in the relative positions of said threads as shown in the corresponding adjacent Figures 5, 6 and 7 The sewing machine illustrated in the drawings is of the type more' particularly adapted for stitching leather and the constructive features thereof, aside from the present improvement, are well known in the art. The sewing machine has a framecomprising a bed-plate l, upon one end of which is suitably secured the base-flange 2 of a hollow work-supporting post 3 rising vertically from an opening I in the bed-plate I. Mounted upon the opposite end of the bed-plate I is a hollow standard 4 supporting a gooseneck or bracket-arm which terminates at its free end in a head 6 overhanging the work-supporting post 3.

Rotatably journaled in the bracket-arm 5 is a horizontally disposed main actuating shaft 1 connected in any usual or suitable manner to actuate a vertically disposed needle-bar 8 carrying at its lower end an eye-pointed needle 8, said needlebar being journaled for endwise reciprocation in the bracket-arm head 6.

The arm-shaft I carries a belt-pulley II! con:

nected by a belt II with a belt-pulley 12 of the same size as the pulley Ill, the belt-pulley [2 being carried by a loop-taker and feed-actuating shaft l3 disposed below the bed-plate l in parallelism with the shaft 1 and journaled for rotation in suitable bearings depending from said bed-plate.

The bed-shaft l3, which rotates once for each rotation of the arm-shaft I, carries a bevel-gear [4 in driving engagement with 'a smaller bevel!- gear l5 carried by the lower end of a vertically disposed loop-taker carrying shaft IS, the ratio of the gears I 4 and I5 being such that the looptaker shaft l6 rotates twice for each rotation of the bed-shaft l3. The loop-taker shaft I6 is journaled in vertically spaced bearing-lugs l1 and I8 provided within the work-supporting post ,3, and secured to the upper end of said shaft 16 for rotationtherewith is a loop-taker IQ of the verti cal-axis rotary hook type, said loop-taker I9 being disposed above and in proximity to the upper bearing-lug ll of the post 3.

The loop-taker l9 has the usual cup-shaped body provided with a loop-seizing beak l9 and a loop-discharging tail l9", it being understood that the loop-taker beak l9 rotates in a plane transverse to the path of needle-reciprocation. Journaled in the loop-taker I9 is a thread carrier 20 about which the loop-taker I9 casts loops of needle-thread in the formation of lock-stitches. The thread-carrier 20 is restrained against rotation with the loop-taker and to that end is formed with spaced shoulders 21 and 22 providing therebetween a stop-notch 23 loosely entered by a stationary stop-lug 24 depending from one side edge of a throat-plate 25. The throat-plate 25 is as usual suitably secured upon the upper end of the post 3 and is provided with a needle-aperture 26 and feed-slots 21.

Operating through the feed-slots 21 is a feeddog 28 of the drop-feed type, said feed-dog being opposed by a roller-presser 29 carried by the-,lower end of a spring-depressed presser-barj ll journaled for vertical movement in the bracket arm head 6. The feed-dog 2a is suitably securedupon the upper end of a feed-bar 3| disposed vertically within the post 3 and having intermediate lower end, the feed-bar ii is connected by a pivot-bolt 34 to a carrier-bar 35 intermediate the ends of said carrier-bar. One end of the carrierbar 2' is pivotally connected to an upright feedrocker 38 carried by a feed-advance rock-shaft 31, while the other end of said carrier-bar is formed with a fork is embracing a block 29 pivotally carried b an arm 40 extending generally horizontally from and clamped upon a feed-lift rock-shaft 4!. The rock-shafts 3! and 4| may be actuated in any usual or suitable manner to impart properly timed work-advancing movements to the feed-dog 20.

The thread-carrier shoulder 2! is disposed at the side of the stop-lug 24 at which the needlethread loops are initially cast about the threadcarrier 24. Adapted intermittently to engage the thread-carrier shoulder 2i to slightly oscillate the thread-carrier in a direction opposite to the direction of rotation of the loop-taker i9 is the horizontally bent free end portion of a vertically disposed arm 42 of an angular lever 42,, 42. Intermediate its ends, the lever referred to has an aperture 44 entered by a pivot-screw 45 threaded horizontally into the post-lug II. The horizontally extending arm 43 of the lever is pivotally connected by a pivot-pin 46 to a collar 41 secured by a screw 48 for vertical adjustment upon the upper end portion of an actuating bar 48. The bar 49 has vertically directed endwise movements within the post 3, the lower end of said bar being rigidly connected to a strap l embracing an eccentric carried by'the bed-shaft i3. Consequently, the lever 42, 43 performs one complete oscillation about its horizontal pivot-axis for each complete reciprocation of the needle.

The thread-carrier 20 has the usual bobbinthread tension-spring I2 to impose a frictional drag upon the bobbin-thread b emerging from said thread-carrier, and the latter also has the usual bobbin-thread guiding eye 53 adjacent said tension-spring 52. The tension-spring 52 and the thread-guiding eye 53 together constitute thread-delivery control means so disposed that the bobbin-thread extends substantially horizontally from the guiding-eye 53 to the throat-plate needle-aperture 26 at an inclination to the line of feed of the work and at the needle-loop caston side of the bobbin-carrier 20. In other words, the lead of the bobbin-thread from the threadguiding eye 53' is substantially tangential to the thread-carrier 20 and is, in general, opposite to the direction of rotation of the loop-taker l9, whereby a pull upon the bobbin-thread b incidental to the feed of the work or otherwise from the throat-plate aperture 26 side of the thread-carrier 20 tends to turn said threadcarrier in a direction opposite to the direction of rotation of the loop-taker.

At the time of seizure of the needle-thread loop by the loop-taker IS, the thread-carrier oscillating arm 42 is spaced, from the bobbin-carrier shoulder 2|, whereby the limb n of the needlethread loop which is cast across the upper face of the thread-carrier 20 by the loop-taker is free to pass between the opener-arm 42 and the bobbin-carrier shoulder 2! at the beginning of the loop-casting operation.

As the needle-loop approaches maximum expansion thereof by the loop-taker, the needleloop limb n engages the bobbin-thread b adjacent the throat-plate needle-aperture 2., as illustrated in Fig. 5 of the drawings. thereby exerting a pressure upon the bobbin-thread in a direction tending to oscillate the thread-carrier oppositely to the direction of rotation of the loop-taker. Oscillation of the thread-carrier in this manner is favorable to stitch-formation, for by reason of the slight oscillation which may thus be imparted to the thread-carrier the bobbin-thread b is slackened sumciently to permit the needle-loop limb n to pass about the bobbinthread b within the throat-plate needle-aperture 26. In this connection, it is to be understood that the bobbin-thread b is normally held by the tension thereof against the rearward wall of the throat-plate needle-aperture 28.

However, the frictional drag imposed by the loop-taker l9 upon the thread-carrier is generally such as to resist oscillation of the threadcarrier in the manner above described. Furthermore, for certain leather stitching operations, it is necessary that the frictional drag imposed upon the'bobbin-thread b by the tension-spring 52 be sufllciently strong to insuredrawing of the bobbin-thread well into the under side of the leather when the stitches are set and, consequently, the requisite looseness of the bobbinthread cannot be provided by drawing some of said thread through its tensioning device by the action of the needle-thread loop upon the bobbin-thread as above described.

In accordance with the present invention, the thread-carrier oscillating arm 42 is actuated to engage the thread-carrier shoulder 2| in substantially the position of the loop-taker l9 illustrated in Fig. 6 of the drawings, i. e., in substantially the position of the loop-taker in which the loop of needle-thread is about to be cast oil from the beak i9 and onto the tall I!" of said looptaker. The lever-arm 42 acts to slightly oscillate the bobbin-carrier 20 in a direction opposite to the direction of rotation of theloop-taker, thereby positively insuring the desired slack in the bobbin-thread b to enable the limb n of the needle-thread loop to pass between the bobbinthread b and the wall of the throat-plate needleaperture 26 against which the bobbin-thread is normally held.

At the same time, the lever-arm 42 acts to shift the thread-carrier shoulder 22 away from the stop-lug 24, against which stop-lug the shoulder 22 is normally held by the friction between the loop-taker l9 and the thread-carrier 20. Consequently, a thread-clearance gap is positively provided between the shoulder 22 and stoplug 24, as illustrated in Fig. 7, permitting the loop-limb n which has now passed about the bobbin-thread b in the throat-plate needle-aperture and under the stop-lug 24 to be drawn through said gap preparatory to final drawing up of said loop by the usual take-up lever I54. The bobbin-thread slack created by the leverarm 42 is absorbed by the subsequent feed of the work so that at the time when the stitch is set the bobbin-thread is again taut between the throat-plate needle-aperture 26 and the bobbincarrier 2!.

The lever-arm 42 begins its return-movement after the loop-limb b has passed through the gap provided by said arm between the thread-carrier shoulder 22 and the stop-lug 24. Consequently the lever-arm 42 holds the thread-carrier shoulder 2i substantially in engagement with the stoplug 24 at the time when the stitches are set. The thread-carrier 20 follows the return movement of the lever-arm 42, due to frictional action there-- upon imposed by the loop-taker, thereby again closing the gap between the shoulder 22 and the stop-lug 24, and at the same time opening a gap between the shoulder 2| and said stop-lug, as well as between the shoulder 2| and the leverarm 42.

It will thus be understood from the foregoing description that the lever-arm 42 not only functions to provide thread-loop clearance between the thread-carrier rotation-restraining elements, but that said lever-arm also acts to improve the loop-casting operation by its control of the tautness of the bobbin-thread at the time when the needle-thread loop is cast about the thread-carrier.

Having thus set forth the nature of the invention, what I claim herein is:

1. In a sewing machine having a throat-plate provided with a, needle-aperture, a rotary looptaker, a thread-carrier journaled in said looptaker and restrained against rotation therewith, a needle reciprocating transversely of the plane of rotation of said loop-taker, and thread-delivery control means provided upon said threadcarrier for the thread contained within the thread-carrier, the improvement whch consists in disposing said thread-delivery control means upon said thread-carrier so that a pull upon the thread delivered thereby and from the throatplate needle-aperture side of the thread-carrier tends to turn said thread-carrier in a direction opposite to the direction of rotation of the looptaker, and means effective during the thread-loop casting rotation of said loop-taker for-positively turning said thread-carrier in a direction opposite to the direction of rotation of said loop-taker.

2. In a sewing machine having a throat-plate provided with a needle-aperture, a rotary looptaker, a thread-carrier journaled in said looptaker and restrained against rotation therewith, a needle reciprocating transversely of the plane of rotation of said loop-taker and thread-delivery control means provided upon said threadcarrier for the thread contained within the thread-carrier, the improvement which consists in disposing said thread-delivery control means upon said thread-carrier at the needle-thread 3. In a sewing machine having a rotary looptaker, a thread-carrier journaled in said looptaker, a needle reciprocating transversely of the plane of rotation of said loop-taker, means for rotating said loop-taker a plurality of times for each complete needle reciprocation, spaced stopshoulders provided upon said thread-carrier and defining therebetween a stop-notch, a stationary stop-lug disposed between said shoulders for restraining said thread-carrier against rotation with said loop-taker, and thread-delivery control means provided upon said thread-carrier for the thread contained within the thread-carrier, the improvement which consists in disposing said thread-delivery control means at the needlethread loop cast-on side of said thread-carrier, an actuated arm engageable with one of said stop-shoulders for turning said thread-carrier in a direction opposite to the direction of rotation of said loop-taker, and means for actuating said arm for turning said thread-carrier once only for each complete needle-reciprocation.

4. In a sewing machine having a frame including a vertically disposed work-supporting post, a vertically reciprocatory needle, 2. vertical-axis rotary loop-taker disposed within the upper end 0! said post and complemental to said needle in the formation of lock-stitches, means for rotating said loop-taker a plurality of times for each complete needle-reciprocation, and a thread-carrier journaled in said loop-taker and restrained against rotation therewith, the improvement which consists in means for oscillating said thread-carrier in a direction opposite to the direction of rotation of said loop-taker comprising a lever adapted intermittently to engage said thread-carrier, a. bar connected to actuate said lever and endwise reciprocable lengthwise of said post, and means for reciprocating said bar once only for each needle-reciprocation.

SYDNEY zomsi 

